Understanding ScienceWhat is science?

The last time that you watched squirrels play in a park or in your yard, did you realize that you were practicing science? Every time you observe the natural world, you are practicing science. Science is the investigation and exploration of natural events and of the new information that results from those investigations.

When you observe the natural world, you might form questions about what you see. While you are exploring those questions, you probably use reasoning, creativity, and skepti-cism to help you find answers to your questions. People use these behaviors in their daily lives to solve problems, such as how to keep a squirrel from eating bird seed, as shown in Figure 1. Similarly, scientists use these behaviors in their work.

Scientists use a reliable set of skills and methods in different ways to find answers to questions. After reading this chapter, you will have a better understanding of how science works, the limitations of science, and scientific ways of thinking. In addi-tion, you will recognize that when you practice science at home or in the classroom, you use scientific methods to answer ques-tions just as scientists do.

Lesson 1

Figure 1 Someone used reasoning and creativity to design each of these squirrel-proof bird feeders. However, some solutions don’t work. Scientists use similar methods to try to solve problems.

Reading GuideKey Concepts ESSENTIAL QUESTIONS

• What is scientific inquiry?

• What are the results of scientific investigations?

• How can a scientist minimize bias in a scientific investigation?

Vocabulary scienceobservationinferencehypothesispredictiontechnologyscientific theoryscientific lawcritical thinking

Multilingual eGlossarygg

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Life ScienceBiology, or life science, is the study of all living things. This forest ecologist, a life scientist who studies interactions in forest ecosystems, is studying lichens growing on Douglas firs. Biologists ask questions such as

• How do plants produce their own food?

• Why do some animals give birth to live young and others lay eggs?

• How are reptiles and birds related?

Earth ScienceThe study of Earth, including its landforms, rocks, soil, and forces that shape Earth’s surface, is Earth science. These Earth scientists are collecting soil samples in Africa. Earth scientists ask questions such as

• How do rocks form?

• What causes earthquakes?

• What substances are in soil?

Physical ScienceThe study of chemistry and physics is physical science. Physical scientists study the interactions of matter and energy. This chemist is preparing antibiotic solutions. Physical scientists ask questions such as

• How do substances react and form new substances?

• Why does a liquid change to a solid?

• How are force and motion related?

Branches of Science No one person can study all the natural world. Therefore,

people tend to focus their efforts on one of the three fields or branches of science—life science, Earth science, or physical science, as described below. Then people or scientists can seek answers to specific problems within one field of science.

WORD ORIGINbiologyfrom Greek bios, means “life”; and logia, means “study of”

Chapter 1/Scientific Explanations 5

Modify/Revise Hypothesis

Figure 2 This flow chart shows steps you or a scientist might use during a scientific investigation.

Visual Check What happens if a hypothesis is not supported?

Ask Questions• Make observations• State a problem• Gather information• Infer

Hypothesizeand

Predict

Test Hypothesis• Design an experiment• Make a model• Gather and evaluate

evidence• Collect data/record

observations

Repeat several times to confirmFertilizing the soil will

cause the tomatoes to grow more quickly.

Scientific InquiryAs scientists study the natural world, they

ask questions about what they observe. To find the answers to these questions, they usually use certain skills, or methods. The chart in Figure 2 shows a sequence of the skills that a scientist might use in an investi-gation. However, it is important to know that, sometimes, not all of these skills are performed in an investigation, or performed in this order. Scientists practice scientific inquiry— a process that uses a variety of skills and tools to answer questions or to test ideas about the natural world.

Ask Questions Like a scientist, you use scientific inquiry

in your life, too. Suppose you decide to plant a vegetable garden. As you plant the vegeta-ble seeds, you water some seeds more than others. Then, you weed part of the garden and mix fertilizer into some of the soil. After a few weeks, you observe that some vegeta-ble plants are growing better than others. An observation is using one or more of your senses to gather information and take note of what occurs.

Observations often are the beginning of the process of inquiry and can lead to ques-tions such as “Why are some plants growing better than others?” As you are making observations and asking questions, you recall from science class that plants need plenty of water and sunlight to grow. Therefore you infer that perhaps some vegetables are receiv-ing more water or sunlight than others and, therefore, are growing better. An inferenceis a logical explanation of an observation that is drawn from prior knowledge or experience.

Hypothesize After making observations and inferences,

you are ready to develop a hypothesis and investigate why some vegetables are growing better than others. A possible explanation about an observation that can be tested by scientific investigations is a hypothesis. Your hypothesis might be: Some plants are grow-ing taller and more quickly than others because they are receiving more water and sunlight. Or, your hypothesis might be: The plants that are growing quickly have received fertilizer because fertilizer helps plants grow.

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Hypothesis not supported

Predict After you state a hypothesis, you might

make a prediction to help you test your hypothesis. A prediction is a statement of what will happen next in a sequence of events. For instance, based on your hypotheses, you might predict that if some plants receive more water, sunlight, or fertilizer, then they will grow taller and more quickly.

Test your Hypothesis When you test a hypothesis, you often

are testing your predictions. For example, you might design an experiment to test your hypothesis on the fertilizer. You set up an experiment in which you plant seeds and add fertilizer to only some of them. Your pre-diction is that the plants that get the fertil-izer will grow more quickly. If your prediction is confirmed, it supports your hypothesis. If your prediction is not confirmed, your hypothesis might need revision.

Analyze ResultsAs you are testing your hypothesis, you

are probably collecting data about the plants’ rates of growth and how much fertilizer each plant receives. Initially, it might be difficult to recognize patterns and relationships in data. Your next step might be to organize and analyze your data.

You can create graphs, classify informa-tion, or make models and calculations. Once data are organized, you more easily can study the data and draw conclusions. Other meth-ods of testing a hypothesis and analyzing results are shown in Figure 2.

Draw ConclusionsNow you must decide whether your data

support your hypothesis and then draw con-clusions. A conclusion is a summary of the information gained from testing a hypothe-sis. If your hypothesis is supported, repeat your experiment several times. A repeated experiment is performed by the same scien-tist and ensures that results are accurate. If your hypothesis is not supported, you can modify it and repeat the scientific inquiry process.

Communicate ResultsScientists communicate new information

to others by writing scientific articles, speak-ing at conferences, or exchanging informa-tion. Other scientists can use this new information in their research. This is also how other scientists learn of experiments that need to be replicated. During experi-ment replication, different scientists repeat an experiment to verify results.

Analyze Results• Graph results• Classify information• Make calculations• Other processes

Draw Conclusions

• Infer• Reasoning

Communicate Results• Write science journal articles• Speak at science conferences• Exchange information on Internet• Other ways of exchanging information

Hypothesis supported

Tomato Plant HeightHeight (cm)

432

17.710.1

5.32.51

Week

Data Table

Chapter 1/Scientific Explanations 7

Results of Scientific InquiryBoth you and scientists perform scientific inquiry to find answers

to questions. There are many outcomes of scientific inquiry, such as technology, materials, and explanations, as shown below.

Key Concept Check What are the results of scientific investigations?

Technology The practical use of scientific knowledge, especially for industrial or commercial use is technology. Televisions, MP3 players, and computers are examples of technology. The C-Leg, shown to the right, is one of the latest designs of computer-aided limbs. The prosthetic leg has sensors that anticipate the user’s next move, which prevents him or her from stumbling or tripping. In addition, this new technology has several modes that can enable the user to walk, stand for long periods of time, and even ride a bike.

New MaterialsAnother possible outcome of an investigation is a new material. For example, scientists have developed a bone bioceramic. A bioceramic is a natural calcium-phosphate mineral complex that is part of bones and teeth. This synthetic bone mimics natural bone’s structure. Its porous structure allows a type of cell to grow and develop into new bone tissue. The bioceramic can be shaped into implants that are treated with certain cells from the patient’s bone marrow. It then can be implanted into the patient’s body to replace missing bone.

Possible Explanations Many times, scientific investigations answer the questions: who, what, when, where, or how. For example, who left fingerprints at a crime scene? When should fertilizer be applied to plants? What organisms live in rain forests?

In 2007, while exploring in Colombia’s tropical rain forests, scientists discovered a new species of poisonous tree frog. The golden frog of Supatá is only 2 cm long.

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Table 1 Comparing Scientific Theory and Scientific Law

Scientific Theory Scientific Law

A scientific theory is based on repeated observations and scientific investigations.

Scientific laws are observations of similar events that have been observed repeatedly.

If new information does not support a scientific theory, the theory will be modified or rejected.

If many new observations do not follow the law, the law is rejected.

A scientific theory attempts to explain why something happens.

A scientific law states that something will happen.

A scientific theory usually is more complex than a scientific law and might contain many well-supported hypotheses.

A scientific law usually is based on one well-supported hypothesis that states that something will happen.

Make a vertical two-column chart book. Label it as shown. Use it to organize your notes on scientific investigations.

Figure 3 When you view blood using a microscope, you will see that it contains red blood cells.

ExamplesResults ofScientific

Investigations

Scientific Theory and Scientific LawsScientists often repeat scientific investigations to verify that

the results for a hypothesis or a group of hypotheses are cor-rect. This can lead to a scientific theory.

Scientific Theory The everyday meaning of the word theory is an untested idea or an opinion. However, a scientific theory is an explanation of observations or events based on knowledge gained from many observations and investigations. For example, about 300 years ago, scientists began looking at samples of trees, water, and blood through the first microscopes. They noticed that all of these organisms were made of tinier units, or cells, as shown in Figure 3. As more scientists observed cells in other organisms, their observations became known as the cell theory. This theory explains that all living things are made of cells. A scientific theory is assumed to be the best explanation of obser-vations unless it is disproved. The cell theory will continue to explain the makeup of all organisms until an organism is dis-covered that is not made of cells.

Scientific Laws Scientific laws are different from societal laws, which are agreements on a set of behaviors. A scientific law describes a pattern or an event in nature that is always true. A sci-entific theory might explain how and why an event occurs. But a scientific law states only that an event in nature will occur under specific conditions. For example, the law of con-servation of mass states that the mass of materials will be the same before and after a chemical reaction. This scientific law does not explain why this occurs—only that it will occur. Table 1 compares a scientific theory and a scientific law.

Chapter 1/Scientific Explanations 9

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Skepticism in MediaWhen you see scientific issues in the media, such as news-

papers, radio, television, and magazines, it is important to be skeptical. When you are skeptical, you question information that you read or hear, or events you observe. Is the information truthful? Is it accurate? It also is important that you question statements made by people outside their area of expertise, and claims that are based on vague statements.

Evaluating Scientific EvidenceAn important skill in scientific inquiry is critical thinking.

Critical thinking is comparing what you already know with the information you are given in order to decide whether you agree with it. Identifying and minimizing bias also is important when conducting scientific inquiry. To minimize bias in an investiga-tion, sampling, repetition, and blind studies can be helpful, as shown below .

Key Concept Check How can a scientist minimize bias in a scientific investigation?

2 Bias

It is important to reduce bias during scientific investigations. Bias is intentional or uninten-tional prejudice toward a specific outcome. Sources of bias in an investigation can include equipment choices, hypothesis formation, and prior knowledge.

Suppose you were a part of a taste test for a new cereal. If you knew the price of each cereal, you might think that the most expensive one tastes the best. This is a bias.

1 Sampling

A method of data collection that involves studying small amounts of something in order to learn about the larger whole is sampling. A sample should be a random representation of the whole.

3 Blind Study

A procedure that can reduce bias is a blind study. The investigator, subject, or both do not know which item they are testing. Personal bias cannot affect an investigation if partici-pants do not know what they are testing.

4 Repetition

If you get different results when you repeat an investiga-tion, then the original investigation probably was flawed. Repetition of experiments helps reduce bias.

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Science cannot answer all questions.You might think that any question can be answered through

a scientific investigation. But there are some questions that sci-ence cannot answer, such as the one posed in Figure 4. Questions about personal opinions, values, beliefs, and feelings cannot be answered scientifically. However, some people use scientific evidence to try to strengthen their claims about these topics.

Safety in ScienceScientists follow safety procedures when they conduct inves-

tigations. You too should follow safety procedures when you do any experiments. You should wear appropriate safety equip-ment and listen to your teacher’s instructions. Also, you should learn to recognize potential hazards and to know the meaning of safety symbols. Read more about science laboratory safety in the Science Skill Handbook at the back of this book.

Ethics are especially important when using living things during investigations. Animals should be treated properly. Scientists also should tell research participants about the poten-tial risks and benefits of the research. Anyone can refuse to participate in scientific research.

Use Vocabulary1 Explain the relationship between

observations and hypotheses.

2 Use the terms technology, scientific law, and scientific theory in complete sentences.

3 Contrast inference and prediction.

4 Compare and contrast critical thinking and inference.

Understand Key Concepts 5 Which should NOT be part of scientific

inquiry?A. bias C. hypothesisB. analysis D. testing

6 Describe four real-life examples of the results of scientific investigations.

7 Discuss four ways a scientist can reduce bias in scientific investigations.

Interpret Graphics8 Draw a graphic organizer like the one

below. In each oval, list an example of how to test a hypothesis using scientific inquiry.

Test Hypothesis

Critical Thinking9 Suggest Why do you think people

believe some theories even if they are not supported by credible evidence?

10 Evaluate In a magazine, you read that two scientific investigations attempted to answer the same question. However, the two teams of scientists came to opposite conclusions. How do you decide which investigation was valid?

Lesson 1 Review

Figure 4 Science cannot answer questions based on opinions or feelings, such as which paint color is the prettiest.

ACADEMIC VOCABULARYethics(noun) rules of conduct or moral principles

Online QuizAssessment

Virtual LabInquiry??

Chapter 1/Scientific Explanations 11